Remove integer keys from lush table, use string lookups (issue #29)

VM now resolves lush functions via luaH_getshortstr through interned
TString pointers, so wrapping lush.command = my_wrapper is transparently
picked up. The lush table no longer has integer-keyed duplicates.

lvm.c

@@ -30,6 +30,7 @@
 #include "ltable.h"
 #include "ltm.h"
 #include "lvm.h"
+#include "lcmd.h"
 
 
 /*
@@ -1947,7 +1948,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         lu_byte tag = luaH_getint(regt, LUA_RIDX_LUSH, &lushtv);
         if (novariant(tag) == LUA_TTABLE) {
           TValue func;
-          luaH_getint(hvalue(&lushtv), idx + 1, &func);  /* 1-based */
+          luaH_getshortstr(hvalue(&lushtv), lushname[idx], &func);
           setobj2s(L, ra, &func);
         }
         vmbreak;